Realpolitik is a political system that's not based on beliefs, doctrines, ethics, or morals, but rather on realistic, practical ideas. Richard Nixon's diplomacy with China in the 1970's was an example of realpolitik.
Realpolitik is put into practice when governments deal in straightforward, goal-oriented ways with other governments. Nixon's conversations with the communist Chinese government are such a good example of realpolitik because he felt diplomacy was important despite Americans' distrust of communism. The word realpolitik, coined in 1914, comes directly from German, in which it literally means "practical politics."